(a) Field of the Invention
The present invention relates to a system for controlling a motor of a hybrid vehicle. More particularly, the present invention relates to a system for controlling a motor of a hybrid vehicle that can secure robustness and stability of control by selecting an optimal approximation model according to a driving condition of the motor and determining current order for controlling the motor by using the selected optimal approximation model.
(b) Description of the Related Art
Recently, environmentally-friendly vehicles such as hybrid vehicles and electric vehicles have attracted increasing attention due to energy depletion and environmental pollution. These environmentally-friendly vehicles typically include a motor generating driving torque by using electrical current from a battery. According to a conventional method for controlling the motor, a demand torque according to the current driving conditions of the vehicle is calculated and an operating current for generating and producing the demand torque is calculated so that the operating current can be applied to the motor.
However, operation of the motor is greatly affected by the motor temperature and an inverter voltage (i.e., input voltage). Therefore, the operating current is generally corrected according to the motor temperature and the inverter voltage. That is, the operating current is primarily corrected by the motor temperature and is secondarily corrected by the inverter voltage.
According to a conventional method that corrects the operating current according to the motor temperature, a map according to the driving condition of the vehicle is set at every reference temperature of the motor, and a compensation value of the operating current is calculated by substituting the driving condition of the vehicle into the map that corresponds to a respective reference temperature. If the motor temperature is not a predetermined reference temperature, the first and second reference temperatures closest to the motor temperature are selected, compensation values of the first and second operating currents are calculated from the maps according to the first and second reference temperatures, and the compensation value of the operating current is calculated from the compensation values of the first and second operating currents by interpolation.
Since one map is required at each reference temperature according to a conventional method that primarily corrects the operating current using the motor temperature, a plurality of maps are created so as to secure control reliability. Therefore, since a great many experiments are performed and a significant amount of time is required to create these maps, development costs are higher than most manufactures would like.
Even further, according to a conventional method that secondarily corrects the operating current by the inverter voltage, a motor speed is normalized according to the inverter input voltage and the compensation value of the current is calculated according to the normalized motor speed. Since voltage usage efficiency of the motor, however, is changed according to a load condition of the vehicle, control reliability may be deteriorated. In order to secure control reliability, weight value according to the load condition of the vehicle should be calculated as well.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.